1. Field of the Invention
This invention relates to an optical fiber connector which transmits only light having selected wavelengths, and an optical density measuring system in which the optical fiber connector is employed.
2. Description of the Prior Art
Quantitative or qualitative analysis of a specific component in a sample liquid is a common operation carried out in various industrial fields. Especially, quantitative analysis of a chemical component or a solid component contained in body fluid such as blood or urine is very important in the field of clinical biochemistry.
There has been put into practice a dry-type chemical analysis slide with which a specific component contained in a sample liquid can be quantified through a droplet of the sample liquid deposited on the slide. See Japanese Patent Publication No. 53(1978)-21677, Japanese Unexamined Patent Publication No. 55(1980)-164356 or the like. When such a dry-type chemical analysis slide is used, the sample liquid can be analyzed more easily and more quickly than when the conventional wet analysis method is used, and accordingly the dry-type chemical analysis slide is very convenient for medical facilities, laboratories and the like where lots of sample liquids have to be analyzed.
When chemical components or the like contained in a sample liquid is analyzed using such a dry-type chemical analysis slide, a droplet of the sample liquid is deposited on the slide and is held at a constant temperature for a predetermined time in an incubator so that coloring reaction occurs, and the optical density of the color formed by the coloring reaction is optically measured. That is, measuring light containing a wavelength which is pre-selected according to the combination of the component to be analyzed and the reagent contained in the reagent layer of the slide is projected onto the slide and the optical density of the reflected light is measured. Then the component to be analyzed is quantified on the basis of the optical density of the reflected light by colorimetry.
In medical facilities, laboratories and the like where lots of sample liquids are analyzed, it is preferred that a plurality of sample liquids can be analyzed automatically and sequentially. Accordingly, there have been proposed various systems for sequentially effecting analysis of a plurality of sample liquids using the dry-type chemical analysis slides, as disclosed in Japanese Unexamined Patent Publication No. 56(1981)-777746, for instance. Further, there has been proposed in U.S. Pat. No. 3,526,480 a system which enables automatic and sequential analysis of a plurality of sample liquids by the use of a test film in a continuous length bearing thereon a reagent layer. In the system, the deposition of droplets of a plurality of sample liquids on the test film, the incubation of the droplets, and the measurement of the optical density of the reflected light are sequentially carried out while the test film is intermittently conveyed. The system using the test film in continuous length is advantageous over the system using the slides in that the running cost is lower and lots of sample liquids can be sequentially analyzed with a simple mechanism.
In the biochemical analysis system using either the slides or the test film, the optical density of the reflected light is measured with a reflection density measuring system. The reflection density measuring system generally comprises a light projecting means which projects measuring light onto a specimen, and a photodetector which detects light reflected at the specimen. As the light projecting means, there has been known one which comprises a light source and an optical fiber means which transmits light emitted from the light source to the specimen. (See Japanese Unexamined Patent Publication No. 62(1987)-245241, for instance.) Such a light projecting means is advantageous in that the light emitted from a single light source can be projected onto a plurality of specimens at one time by the use of a plurality of optical fiber means, and the light source can be relatively freely positioned with respect to the position of the specimens.
The light source generally comprises a tungsten lamp which emits light having a relatively wide wavelength range. On the other hand, the wavelength most effective to the measurement differs depending on the component of the sample liquid to be analyzed. That is, when light having a particular wavelength is projected onto the specimen, the change in the quantity of the reflected light from the specimen with change of the concentration of a given component in the sample liquid is maximized, and the particular wavelength of the light which causes the maximum change in the quantity of the reflected light changes depending on the kind of the component in the sample liquid. For example, the "particular wavelength" for glucose is about 510 nm. When only light having the particular wavelength is projected onto the specimen according to the given component to be analyzed in the specimen, the concentration of the component can be measured most effectively. Light having a selected wavelength can be projected onto the specimen by the use of an optical filter which transmits only the light having the selected wavelength. The optical filter may be an interference filter, for instance, and may be disposed near the light source or the light emanating end of the optical fiber means, for instance.
Since, there are a plurality of components to be analyzed and in order to effectively accomplish the measurement of the optical density, the optical filter must be changed according to the component to be analyzed. However, the part of the reflection density measuring system near the light source and the part near the light emanating end to the optical fiber means are generally difficult of access.